Douglas S. Goodman
The ordinary security door peeper, or door viewer, has a number of uses—pedagogical, practical, and fun. This article presents a range of demonstrations using door peepers. For many of these demonstrations, the essential feature of the door peeper is that it compresses an entire hemisphere of phenomena into an angle small enough to fit the retina, so things that vary over a wide range of angles can be comprehended in a single view.
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